In contrast with healthy controls, high psychopathic individuals appear deficient in the capacity to form appropriate associations between a cue and an aversive (Hare et al., 1978, Flor et al., 2002) or fear-evoking event (Patrick et al., 1994, Birbaumer et al., 2005)—despite intact cognitive processing of stimuli (Flor et al., 2002, Birbaumer et al., 2005, Kiehl, 2006).
In healthy individuals, aversive or threatening cues result in the mobilization of defensive actions, which can be measured by fear-associated responses such as the startle reflex that increase during presentation of aversive stimuli (Davis, 1989, Lang et al., 1990, Patrick et al., 1996). In psychopathic individuals, who are theorized to lack the ability to anticipate and learn from punishment (Lykken, 1957, Hare and Quinn, 1971, Hare et al., 1978, Veit et al., 2002, Blair, 2004, Birbaumer et al., 2005, Mitchell et al., 2006), the fear-associated startle reflex has been found to be diminished or absent (Patrick et al., 1993, Levenston et al., 2000, Pastor et al., 2003, Benning et al., 2005). Startle potentiation in response to aversive events (Davis, 1992, Angrilli et al., 1996, Pissiota et al., 2003) as well as an anticipatory skin conductance response (Bechara et al., 1999) are known to be mediated by amygdalar connections, suggesting a deficit in the amygdala or affiliated structures in psychopathic individuals.